Human impacts on fire history and forest structure over 1300 years in the Sierra Nevada
/The increased frequency of large, destructive wildfires in the Sierra Nevada has been in part driven by historical management decisions that have altered the structure of forests, creating dense stands dominated by shade tolerant species with thick, flammable understory fuels. Prior to European settlement c. 1850 and the onset of fire suppression policies, abundant archaeological evidence suggests that Indigenous groups occupying the Sierra National Forest (SNF) set frequent, low-intensity fires to maintain “park-like” woodlands with clear travel corridors, productive food and game forage patches, and culturally-important plant materials such as basket-weaving grasses and oak acorns. The history of frequent fire in the SNF has been documented in the paleorecord over at least the past 1700 years as fire scars on tree rings. To this point, this fire history and coincident and subsequent shifts in forest structure have been largely attributed to climate and lightning trends rather than anthropogenic causes, even though Native Americans occupied the area since at least 6000 B.C.E. This discrepancy may be partly due to the low-intensity, slow-moving nature of Indigenous burning, potentially reducing the likelihood of scarring trees and producing sedimentary charcoal. Partitioning the effects of human vs. climatically-induced fire on Sierra Nevada forests over time is essential for understanding baseline forest structures pre-fire suppression and guiding modern restoration.
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Klimaszewski-Patterson, Anna, Theodore Dingemans, Christopher T. Morgan, and Scott A. Mensing. 2024. Human Influence on Late Holocene Fire History in a Mixed-Conifer Forest, Sierra National Forest, California. Fire Ecology 20 (1): 3. doi:10.1186/s42408-023-00245-9.
